Feedback on mathlib-fp 1.9

Use the focused 1.9 feedback form when the library works incorrectly or when the first-use path is harder than it should be. Choose the closest category:

• installation took longer than expected or a documented command failed;
• it was unclear which real/complex, dense/sparse, or compatibility type to use;
• a workflow required boilerplate container conversions;
• an exception, status, or validation message was unexpected or unhelpful;
• selection guidance did not identify the right algorithm;
• migration from an earlier mathlib-fp API was unclear or failed.

Include the release, OS/CPU, FPC version, exact command, observed output, and the result you expected. A small reproducer is especially useful, but feedback about a confusing choice does not require a complete program. Do not post a private vulnerability in a public issue; follow SECURITY.md instead.